Transcript Normal red cell destruction

Blood Biochemistry
Composition of Blood
 Blood
is the body’s only fluid tissue
 It is composed of liquid plasma and formed
elements
 Formed elements include:
Erythrocytes, or red blood cells (RBCs)
Leukocytes, or white blood cells (WBCs)
Platelets
– the percentage of RBCs out of
the total blood volume
 Hematocrit
Components of Whole Blood
Plasma
(55% of whole blood)
1 Withdraw blood
and place in tube
2 Centrifuge
Buffy coat:
leukocyctes and
platelets
(<1% of whole blood)
Erythrocytes
(45% of whole blood)
Formed
elements
Plasma

The blood fraction obtained after removal of the
cellular components

About 77%-81% in the total blood values

Hydrometer is 1.050-1.060, pH is 7.35-7.45, osmotic
pressure is 770kPa (37°C) in the normal human

relevant to coagulation factors, immunoglobulins
and complements
Serum

The blood fraction after separation of the protein
fibrinogen from plasma

Generally obtained by allowing the blood to clot

In this process, fibrinogen is converted to an
insoluble protein, fibrin, which is easily removed

Serum does contain some degradation products of
clotting factors
Plasma composition
Clotting factors
Liquid: water
protein
plasma
Nonprotein nitrogen (NPN)
Serum
solids
Low-molecular-weight
organic substances such as
Serum solids glucose, lipids,
vitamins, hormones and so on
Na+, K+, Ca2+, Mg2+
electrolytes
Gases:O2, CO2
CI-, HCO32-, HPO42-
Non-Protein Notrogen (NPN)

Non-protein nitrogenous compounds
urea, uric acid, creatinine, creatine, nucleotides, amino acids,
bilirubin, polypeptides, glutathione and many others

The Concentration of NPN
14.28~24.99 mmol/L, 50% of NPN is blood urea nitrogen
(BUN)

Source of NPN
derived from the metabolism of nucleic acid and proteins

Excretion of NPN
transported to the kidneys fro excretion from the urin

Significance
act as an index of renal function
 Male
versus female
Hematocrit (% volume that is red
cells)
40-50% in males
35-45% in females
Function of Blood

Blood as a transport system
transport nutrients and oxygen to the cells and
carries away cellular waster products

Blood as a regulative system
maintaining normal acid-base balance in the body;
Regulating the water balance and body temperature

Blood as a defense system
white blood cells and the circulating antibodies

Coagulation and fibrinolysis
Section 1
Plasma Proteins
Plasma Proteins
 More
than 200
 Most abundant
Albumin - 4-5 g/100 mL
g-glubulins - ~1 g/100 mL
fibrinogen - 0.2-0.4g/100 mL
 Original
classification by zone electrophoresis
at pH 8.6
 Separation by pI with several molecular weight
species within each group
Zone Electrophoresis of Plasma
Proteins
+
globulins
g
pI
6.0
b
a1 a2
5.6
5.1
albumin
4.7
Protein Separation

Size Exclusion Chromatography (SEC)
 Porous matrix (sephadex)
 Affinity
chromatography
molecule attached to a
column that
specifically binds the
protein of interest
Coenzyme /
enzyme
Antigen / Antibody
 SDS-PAGE
(polyacrylamide gel
electrophoresis)
Separates by size
Proteins are complexed with SDS to give the
same charge density
Two Dimensional Electrophoresis
Decreasing Mr
Decreasing pI
Characteristics of Plasma Proteins






Most plasma proteins are synthesized in the liver,
however, certain proteins are synthesized in other sides
Generally synthesized on membrane –bound
polyribosomes
With the exception of albumin, almost all plasma
proteins are glycoproteins
Many plasma proteins exhibit polymorphism
Each plasma protein has a characteristic half-life in the
circulation
The levels of certain proteins in plasma increase during
acute inflammatory states or secondary to certain types
of tissue damage
Functions of Plasma Proteins
(1) Functional enzymes of the plasma
 Have
catalysis in the plasma, such as
thrombin, lipoprotein lipase, LCAT etc
(2) non-functional enzymes of the plasma
 Maintenance
of:
Colloid osmotic pressure (COP) (p)
pH
electrolyte balance
 COP
relates to blood volume
DP = p
Protein
sol’n
Water
 Transport
of ions, fatty acids, steroids,
hormones etc.
Albumin (fatty acids), ceruloplasmin (Cu2+),
transferrin (Fe), lipoproteins (LDL, HDL)
 Nutritional source of amino acids for tissues
 Hemostasis (coagulation proteins)
 Prevention of thrombosis (anticoagulant
proteins)
 Defense against infection (antibodies,
complement proteins)
Albumin
MW 66 000
 Single chain, 580 amino acids, sequence is known
 Dimensions - Heart shaped molecule
 50% a helix [He and Carter, Nature, 358 209 (1992)]
 Modeled as:

80 Å
30 Å
Synthesis
Mainly liver cells then exported
Assembly time on ribosome ~ 1-2 min
t0.5 in circulation - 19 days
14 g lost per day
0.4 mg synthesized per hour per g of liver
Need liver of approximately 1.5 kg in weight
to maintain
Functions
Maintaining colloid osmotic pressure of blood
(80% due to albumin)
Colloid osmotic pressure is generated by plasma
proteins
The most abundant of the plasma proteins
The lowest molecular weight of the major protein
molecules in the plasma
High negative charge
Regulates water distribution
Transportation
Albumin can act as a carrier molecule for bilirubin,
fatty acids, trace elements and many drugs
Section 3
Metabolism of the Blood Cells
Cellular Elements of Blood

Red cells
40 - 50% of blood volume
5 x 106 cells /mL
Composed of a membrane surrounding a solution
of hemoglobin
non-nucleated, no intracellular organelles
no proliferation
cell membrane in excess so that deformation
does not rupture
Shape
Biconcave disc
8 mm in diameter, 2.7 mm thick, volume ~ 90
mm3, area ~ 160 mm2
Scanning Electron Micrograph of Red Blood Cells
Why this shape?
Area to volume ratio is high
Facilitates diffusion of O2 and CO2
minimal distance of contents from surface
Originates in bone marrow
(hematopoiesis)
Molecular explanation based on the
properties of the proteins in the cell
membrane is found in Elgsaeter et al.
Science, 234, 1217 (1986)
Production of Erythrocytes
– blood cell formation
 Hematopoiesis occurs in the red bone
marrow of the:
 Hematopoiesis
Axial skeleton and girdles
Epiphyses of the humerus and femur
 Hemocytoblasts
elements
give rise to all formed
Production of Erythrocytes:
Erythropoiesis
A hemocytoblast is transformed into a committed
cell called the proerythroblast
 Proerythroblasts develop into early erythroblasts
 The developmental pathway consists of three
phases

 Phase 1 – ribosome synthesis in early erythroblasts
 Phase 2 – hemoglobin accumulation in late
erythroblasts and normoblasts
 Phase 3 – ejection of the nucleus from normoblasts and
formation of reticulocytes

Reticulocytes then become mature erythrocytes
Production of Erythrocytes:
Erythropoiesis
Figure 17.5
The major function of the red cells
 Delivering
oxygen to the tissues, helping in the
disposal of carbon dioxide and protons
formed by tissue metabolism
Normal red cell breakdown
haemoglobin
haem
iron
transferrin
globin
protoporphyrin
CO
Expired air
Amino acids
Bilirubin
(free)
Liver
conjugation
erythroblast
Bilirubin glucuronides
Urobilin(ogen)
Urine
Stercobilin(ogen)
faeces
Hemoglobin synthesis



Heme synthesis starts with the condensation of glycine and
succinyl coenzyme A under the action of a rate limiting enzyme
δ-aminolevulinic acid (ALA) synthase.
δ -ALA will be formed.
Pyridoxal phosphate (vit. B6) is a coenzyme for this reaction.
COOH
COOH
H2C
CH2
CH 2NH 2
HSCoA + CO2
H2C
+
C¡«SCoA
CH 2
COOH
ALA synthase
（ Pyridoxal phosphate ） C
O
This step takes place in the mitochondria
O
CH 2NH 2
A series of biochemical reactions will follow.
Two molecules of δ-ALA condense to form a pyrrole
called porphobilinogen (PBG)
COOH
O
OH
CH 2
HO
CH 2
O
O
C
H
C
H
H
N
H
ALA dehydratase
2H2O
H2N
This step occurs in the cytoplasm
N
H
Four PBG condense to form a tetrapyrrole
uroporphyrinogen III.
 UPG III is then converted to coproporphyrinogen.

Deaminase
Four PBG
Linear
tetrapyrrole
UPG III isomeiase
UPG III decarboxylase
coproporphyrinogen
Ⅲ
uroporphyrinogen III
This step occurs in the cytoplasm
Haemoglobin synthesis
CPG then changes to
protoporphyrin which
ultimately combines with
iron in the ferrous state
(Fe2+) to form haem.
 Iron is brought to the
developing red cells by a
carrier protein
( transferrin) which
attaches to special
binding sites on the
surface of these cells.
 Transferrin releases iron
and returns back to
circulation.

Haemoglobin synthesis
 Each
molecule of
haem combines
with a globin chain.
 A tetramer of four
globin chains each
with its own haem
group in a pocket is
formed to make up
a haemoglobin
molecule.
Haemoglobin structure



Haem consists of a
protoporphyrin ring with an
iron atom at its centre.
The protoporphyrin ring
consists of four pyrrole
groups which are united by
methane bridges (=C-).
The hydrogen atoms in the
pyrrole groups are replaced
by four methylene (CH3-),
two vinyl (-C=CH2) and two
propionic acid (-CH2-CH2COOH) groups.
Metabolic Characteristics of Mature Erythrocytes
 Can
not carry out synthesis of nucleic acid
and proteins
 Can not obtain energy by oxidative
phosphorylation of the mitochondria
 ATP is synthesized from glycolysis and is
important in process that help the red blood
cell maintain its biconcave shape and also in
the regulation of the transport of ions and of
water in and out of the cell
 The principal modes of glucose metabolism
are anaerobic glycolysis and the pentosephosphate pathway
Glycolysis
 Obtain
energy by glycolysis of glucose
Utilize 2ATP moleculars, produces 4ATP moleculars
with a net gain of 2ATP
-
The function of ATP
To maintain the correct ion balance, brought about by
the pumping out of sodium in exchange for potassium
To maintain the correct conformation of the cell
To protect against the formation of methaemoglobin
To synthesize NAD+ and glutathione
The pathway of 2,3-bisphosphoglycerate (2,3-BPG)
 Formation
of 2,3-BPG
Glucose
1, 3-BPG
Diphosphoglyceromutase
Phosphoglycerate
kinase
2, 3-BPG
Glycerate 3-phosphate
Diphosphoglycerate phosphatase
Lactate
The role of 2,3-BPG
 Plays
an important role in the binding of
oxygen to hemoglobin in erythrocytes
 Combine with hemoglobin, causing a decrease
affinity of hemoglobin for oxygen
pO2 2,3-DPG (lungs)
Oxyhemoglobin
Hemoglobin
pO2 2,3-DPG (tissues)
(HbO2)
(Hb)
The role of the pentose phosphate pathway
 Produce
the NADH which is essential for the
regeneration of reduced glutathione from
oxidized glutathione
NADP+
2GSH
Glutathione
reductase
NADP++H+
Pentose phosphate pathway
GSSG
The role of glutathione are as follows
The role in the destruction of hydrogen peroxide (H2O2)
in erythrocytes
NADP+
2GSH
Glutathione
reductase
NADP++H+
H2O2
Glutathione
peroxidase
GSSG
2H2O
Reduction of methemoglobin
Methemoglobin does not combine with molecular
oxygen and does not have the function of
transporting oxygen
 Normally, methemoglobin is reduced to the ferrous
state by the NADH-dependent methrmoglobin
reductase

Methrmoglobin reductase
MHb (Fe3+)
½ O2
Hb (Fe2+)
NADH+H+
NAD
H2O
Genetic abnormality-deficiency of glucose-6phosphate dehydrogenase
glucose-6-phosphate dehydrogenase is the first
enzyme of the pentose phosphate pathway
 A deficiency of this enzyme will lead to failure of
restoring GSSG to GSH in the erythrocytes, a step
essential for the removel of H2O2
 Cell damage is likely to result from oxidation of the
membranes by the H2O2, leading to hemolytic
anemia

White Blood Cells (Leukocytes)
Total count - approximately 7000/mL
 Various types

 Neutrophils 62%
 Eosinophils 2.3%
granulocytes
 Basophils 0.4%
 Monocytes 5.3%
 Lymphocytes 30%
 Plasma cells (mainly in the lymph)

Monocytes in tissue become macrophages
 Function
Defense against foreign invaders
bacteria
viruses
foreign materials (including biomaterials)
 Phagocytosis
Neutrophils, macrophages
Move to foreign particle by chemtaxis
Chemicals induce migration
Toxins, products of inflamed tissues,
complement reaction products, blot
clotting products
Response is extremely rapid (approx 1 h)
 Lymphocytes
B cells - responsible for humoral immunity
T cells - responsible for cell mediated
immunity
 B cells responsible for production of
antibodies
Receptor matches antigen
Cells multiply
Antibodies
 Abs are just immunoglobulins discussed
earlier
T cells
Cytotoxic T cells (Killer T cells)
Bind to cytotoxic cells (eg infected by virus)
Swell
Release toxins into cytoplasm
Helper T cells
Most numerous
Activate B cells, killer T cells
Stimulate activity by secretion of IL2
Stimulate macrophages
Suppressor T cells
Regulate activities of other cell types
Erythropoietin Mechanism
Start
Normal blood oxygen levels
Increases
O2-carrying
ability of blood
Stimulus: Hypoxia due to
decreased RBC count,
decreased availability of O2
to blood, or increased
tissue demands for O2
Reduces O2
levels in blood
Enhanced
erythropoiesis
increases RBC
count
Erythropoietin
stimulates red
bone marrow
Kidney (and liver to a
smaller extent) releases
erythropoietin
Figure 17.6
Haemoglobin catabolism
*normal red cell destruction*
Red cell destruction usually occurs after a mean
life span of 120 days.
 The cells are removed extravascularly by
macrophages of the reticuloendothelial system
(RES), specially in the bone marrow but also in the
liver and spleen.
 Red cell metabolism gradually deteriorates as
enzymes are degraded and not replaced, until the
cells become non viable, but the exact reason why
the red cells die is obscure.

Haemoglobin catabolism
*normal red cell destruction*
 The
breakdown of red cells liberates
1- iron for recirculation via plasma transferrin
to marrow erythroblasts
2- protoporphyrin which is broken down to
bilirubin.
3- globins which are converted to amino acids.
Normal red cell destruction
- The bilirubin circulates to the liver where it is
conjugated to glucuronides which are
excreted into the gut via bile and converted
to stercobilinogen and stercobilin(excreted
in faeces).
- Stercobilinogen and stercobilin are partly
reabsorbed and excreted in urine as
urobilinogen and urobilin.
Normal red cell destruction
 A small
fraction of protoporphyrin is
converted to carbon monoxide (CO) and
excreted via the lungs.
 Globin chains are broken down to amino
acids which are reutilized for general protein
synthesis in the body.
Normal red cell breakdown
haemoglobin
haem
iron
transferrin
globin
protoporphyrin
CO
Expired air
Amino acids
Bilirubin
(free)
Liver
conjugation
erythroblast
Bilirubin glucuronides
Urobilin(ogen)
Urine
Stercobilin(ogen)
faeces
Haemoglobin abnormalities
There are mainly two types of abnormalities,
these are :
 Quantitative abnormalities: where there is
reduction in the production of certain types
of globins e.g. a thalassaemia
b thalassaemia
 Qualitative abnormalities: where there is
production of abnormal haemoglobin e.g.
sickle cell anaemia.
Composition and Function of Blood
Blood composition
- 5-6 L in an adult
- 70 mL/kg of body weight
- Suspension of cells in a carrier fluid (plasma
> Cells - 45% by volume (cellular fraction)
> Plasma - 55% by volume (non-cellular
fraction)
Cells
Red cells (erythrocytes)
5x106/mL
White cells (leukocytes)
7x103/mL
Platelets (thrombocytes)
3x105/mL
Oxygen Binding of Hb
 Blood
must carry 600 L of O2 from lungs
to tissues each day
Very little carried in plasma since O2 only
sparingly soluble
Nearly all bound and transported by Hb of
RBC
Possible for Hb to carry four O2 molecules,
one on each a chain, one on each b chain
 O2
depleted Hb solution placed in contact
with O2(g)
 Equilibrium reaction
 Fraction (s) of Hb converted to
oxyhemoglobin